We propose to use novel optical methods to study extrasynaptic GABAA receptors, a subset of inhibitory neurotransmitter receptors implicated in both acute alcohol action and in adaptation to chronic alcohol exposure. These new methods will allow us to examine pools of these receptors that, for technical reasons, have been experimentally inaccessible. Specific aim one proposes to use laser-based photolysis techniques to determine the properties of non- synaptic GABARs in various locations on cerebellar neurons. The second specific aim makes use of a novel optical voltage sensing method to examine GABAR function and pharmacology on axons and presynaptic terminals. The results will facilitate understanding of the molecular determinants of ethanol and sedative action in the brain and should speed the development of new therapies to address alcohol addiction and the chronic changes in brain function that occur during alcoholism. PUBLIC HEALTH RELEVANCE: We propose to use novel optical methods to study extrasynaptic GABAA receptors, a subset of inhibitory neurotransmitter receptors implicated in both acute alcohol action and in adaptation to chronic alcohol exposure. These new methods will allow us to examine pools of these receptors that, for technical reasons, have been experimentally inaccessible. The results will facilitate understanding of the molecular determinants of ethanol action in the brain and should speed the development of new therapies to address alcohol addiction and the chronic changes in brain function that occur during alcoholism.